Field of the Invention
The present invention relates to an image processing apparatus that processes image data for printing.
Description of the Related Art
In printing a multi-gradation image, the image is subjected to binarization processing in conformity with a printing apparatus. However, simply binarizing a multi-gradation image causes an intermediate concentration to be lost and thus decreases the image quality. Hence, various types of binarization processing that allow prevention of a decrease in image quality have been proposed. Error diffusion methods are widely known as representative techniques.
Error diffusion methods have been improved in various ways. In a conventional error diffusion method, particular textures may be generated at or around an intermediate concentration. Accordingly, an image processing apparatus has been proposed that adds random noise to image data so as to make the textures unnoticeable, and that changes a threshold for binarization processing according to the noise so as to prevent the image quality from decreasing due to the noise addition (see patent document 1).    [Patent Document 1] Japanese Laid-open Patent Publication No. 11-328357